Executive functioning (EF) is an umbrella term for neurologically-based skills that have to do with managing oneself in order to achieve a goal. It includes skills such as working memory, inhibitory control, and attention shifting. These skills are necessary for planning and reasoning which are essential to academic achievement in math, science, and all other subjects requiring reading comprehension. Knowing two languages is often associated with EF skills. This may be because both languages are constantly active in the brain, which gives dual language learners (DLLs) many opportunities to cognitively inhibit the language not currently being spoken and attend to the spoken language. Think, for example, of a DLL interacting in a monolingual environment. The DLL must attend specifically to the language in the particular context and ignore the language that is irrelevant. Furthermore, they must suppress producing words in the unrepresented language because the production of an unknown foreign word would be met with surprise and confusion. Because much of this process is managed automatically in the brain, many DLLs may not be aware of the extra inhibition and attentional practice they are experiencing even though it may be contributing to overall EF skill. Some research indicates that in environments where one language is considered essential for academic and personal success, some children experience loss of their home language. Not all children who are exposed to two languages develop proficiency at the same rate or leave Head Start with similar abilities in each language. For example, by the time they reach kindergarten, some children from Spanish speaking homes, attending English immersion Head Start classrooms, seem to be proficient in two languages, while others seem to be most comfortable in a single language. A practical method for monitoring these changes does not currently exist. Furthermore, how these differences influence the development of EF is unclear. Objectives: 1. Test a method for tracking changes in dual language development that will enhance teachers' understanding of developmental trajectories in key areas of academic readiness. 2. Identify how changes in English and home language vocabulary scores influence EF outcomes. 3. Develop strategies to encourage teachers and families to promote children?s dual language development and to build on this dual language use to enhance ongoing EF development.